Tunnel-frame for combustion engines

ABSTRACT

The invention relates to a tunnel-frame for a multi-cylinder internal combustion engine in line or with two or more cylinder banks, having a tunnel opening in the cross walls, the size of which being sufficient for a crank-shaft to be brought in and out from the frame in axial sense through the tunnel opening, the center line of the main bearings being nearby or on the edge of the tunnel, the non-removable half of the main bearing housing being integral with the reinforced edge of the tunnel opening, the half main bearing housing being closed with a separate main bearing cap.

United States Patent [191 Kuoper [451 Aug. 26, 1975 TUNNEL-FRAME FOR COMBUSTION ENGINES [75] Inventor: Jacob Hermanus Kuoper,

Appingedam, Netherlands 22 Filed: Oct. 11, 1973 21 Appl.No.:405,670

[30] Foreign Application Priority Data Oct. 13, 1972 Netherlands 1. 7213895 [52] US. Cl... 123/195 R; 123/195 AC; 123/195 H; 308/23 [51] Int. Cl F021 7/00 [58] Field of Search..... 123/195 R, 195 AC, 195 H; 308/179, 23

[56] References Cited UNITED STATES PATENTS 1,560,342 11/1925 Foster 308/23 32 as 1 i 1 v 1 2,099,852 11/1937 Knudsen 123/195 R 3.528397 8/1970 Scifert 123/195 R 3,769,953 11/1973 Kuhn..... 123/195 R Primary ExaminerManuel A. Antonakas Assistant ExaminerDaniel J. OConnor Attorney, Agent, or FirmBucknam and Archer 57 ABSTRACT The invention relates to a tunnel-frame for a multicylinder internal combustion engine in line or with two or more cylinder banks, having a tunnel opening in the cross walls, the size of which being sufficient for a crank-shaft to be brought in and out from the frame in axial sense through the tunnel opening, the center line of the main bearings being nearby or on the edge of the tunnel, the non-removable half of the main bearing housing being integral with the reinforced edge of the tunnel opening, the half main bearing housing being closed with a separate main bearing cap.

6 Claims, 2 Drawing Figures PATENTED AUEE' 97s TUNNEL-FRAME FOR COMBUSTION ENGINES Apart from very small internal combustion engines, in which the crank-shaft is assembled in certain cases in the frame itself, it is customary with the majority of engine types to introduce the crank-shaft in the frame either from above, from aside or from beneath, and to locate it respectively in a bed by means of main bearing caps on the top side or to suspend the crank-shaft in main bearing caps. In all these cases the engine frame is open in crank-shaft direction to introduce or remove the crank-shaft. This opening must be closed, for which purpose different solutions are employed.

A quite different method, which is seldom used, makes use of a so-called tunnel-frame, in which case a tunnel shaped opening generally located nearby the location of the crank-shaft when in running order, runs through the motor frame. This tunnel is generally shaped to allow an assembled crank-shaft, f.i. with fitted balancing weights, to be brought into the frame and out from it without any disassembling being necessary. There are generally two methods adapted according to which the crank-shaft is carried in the tunnel-frame. One makes use of rolling bearings which have approximately the same diameter as the tunnel, the main bearing journal being merged with the adjacent crank-webs into a circular main bearing disc, which also serves as inner race of the bearing. With the other method the crank-shaft consists of the normal main bearing journals with a crank-web at each side, the main bearing shells being carried in a stationary split disc, with a close fit in the tunnel bore. Also half discs are used, in which case the main bearing is closed with a normal bearing cap, the half disc often being underslung at that side of the tunnel bore, which is closest to the cylinders.

Characteristic for most of the known engines with a tunnel-frame is the fact, that the center line of the crank-shaft coincides with the center line of the tunnel. All these designs are comparitively expensive, because they do consist of several parts with close tolerances, being very critical in respect to the fitting tolerances and strength due to the alternating loadings. This tunnel design can be simplified when the main bearings of the crank-shaft are situated in the edge of the tunnel opening and are closed by the common separate main bearing caps. By doing this the non-removable half of the main bearing housing forms one integral piece with the tunnelframe, the advantages of the last being retained, and therefor mainly the great stiffness of the closed monolytic tunnel-frame. With a separate main bearing cap, of common design, the main bearing can be closed.

As in practise multi-cylinder engines are in the majority, every design should in the first place be adapted to them. In doing so, the multi-cylinder crankshaft, eventually fitted with balancing weights and forged-on flanges at one or both ends, will have in practise a circular envelop.

It is therefore with good reasons that the tunnel will be cylindrical or almost cylindrical, as is the practise hitherto.

Such a design is known from the German Offenlegungsschrift 1.945.831. This specification relates to a very small engine of the type with a small number of cylinders, which generally are air-cooled, and in the power range of approximately hp per cylinder. The tunnel is situated under the crank-shaft, an eventual oil sump still being lower. To arrive nevertheless at a stiff,

monolitical design, one is forced to extend the motor frame or the crank case very deep under the crankshaft center line.

In case of larger engines, with or more hp per cylinder, it is unrealistic to arrive through upscaling at a similar simple design. In fact an engine with so deep a frame could in many cases not be installed in the engine room of a ship. There it is customary not to hold the lubricating oil in the frame or in the oil sump, but in a separate bottom tank between the engine foundations and cross members of the hull of the ship. A less extended frame would then be possible. But this would come in conflict with the necessity to have a approximately constant moment of resistance of the cross section around the tunnel opening.

According to the invention the solution for this problem is a design in which the bore for the main bearing shells of the crank-shaft is situated in the edge of the tunnel opening being distant from the cylinders. Also with the frame according to the invention a high stiffness should be achieved around the tunnel opening, especially at the location with the biggest stress concentrations, i.c. near the edges of the tunnel at the side of the cylinder bank or cylinder banks. It is known from the Dutch patent application 71.07528 amongst others, to interconnect the cross walls in crank-shaft direction at this side viewing the cylinders, by means of two plates. A stiff double walled, basicly closed, tubular girder results, which passes from one side of the engine to the other and stands rectangular to the plane through the center lines of the cylinders and in case of an engine with two or more cylinder banks shows in the middle one or more sharp bends over at least that part of the frame where cylinders are situated. Each'tubular girder consists therefore of an inner and an outer end plate, which can show in the middle a sharp bend and which is always enclosed between two cross walls. Over the length of the engine the subsequent tubular girders form together a long flat box with cross walls inside. By having the edge of the tunnel opening nearest to the cylinders coincide with the underside of the tubular girder, that is with the inner end plate, the frame according to the invention answers to the requirements of having a moment of resistance of the cross walls of approximately constant value around the tunnel-opening, the forces originating from the cylinder head bolts or cylinder head rods being led along logic and shortest ways to the main bearings without un-acceptable stress concentrations.

If the tubular girders can have well-rounded interconnecting openings, they can serve as scavenging-airreceivers in case of two stroke engines.

If the cylinder head rods from the cylinder heads are running through the tubular girder into the inner end plate, the tubular girder will be freed from tensile forces due to the combustion. By merging the reinforced edge of the tunnel opening into the inner end plate, local stress concentrations can be avoided. The reinforced edge of the tunnel also merges into the integral main bearing housing, leading the gas forces from the cylinder head through the cylinder head rods, the inner end plate and the reinforced cross walls, along the shortest way to the main bearings.

Thanks to the size of the engine, the joint in the main bearing housing can be flat, against circular ones in small-sized tunnel-frames.

With reference to the following description of the accompanying drawings, the invention will be particularly described, a two-stroke trunk-piston engine in V-form being chosen as example, but it is stressed that the invention is equally well applicable to other engine types and designs.

FIG. 1 is a common tunnel-frame, as f.i. applied with the engine according to the Dutch patent specification 125.193.

FIG. 2 is a transverse section and partly a front view, of a tunnel-frame according to the invention, applied to a two-stroke trunk piston V-type engine.

FIG. 1 shows for information purposes a known tunnel-frame, as it is applied to a V-type engine, in which the tunnel opening 1 is visible. The center of the tunnel opening coincides with the center line 2 of the crankshaft. The diameter of the opening is such, that an assembled crank-shaft can be brought into and out from the frame through the opening. The tunnel openings are situated in the cross walls 3 of the frame and at least in one of the end walls. The crank-shaft is either carried more or less directly in the tunnelopening by means of rolls, or it is carried by means of auxiliary constructions with its main journals in the tunnel opening. Reaction forces of the rotating masses and combustion forces have to be conducted from the crank-shaft through the main bearings and the cross walls. To garantee that the crank shaft has got a reliable bearing system, the cross walls should not only be sufficiently strong, but also sufficiently stiff. For that purpose there should be allround the tunnel opening a cross section of sufficient resistance. This is due for the locations 4, 5 and 6. The integral half 8 of the main bearing housing is situated in the cross wall 3 and does not need to be a separate part anymore. A very stiff design results. The main bearing housing is closed with a well known separate main bearing cap 9 (FIG. 2); in the main bearing bore the normal bearing shells 10 and 11 are placed. Sufficient stiffness in the plane of the cross walls and all round the edge of the tunnel opening is achieved by strengthening and stiffening this edge by means of a rib 12, which merges smoothly at 13 at the crank-shaft side into the part 14, which constitutes the integral main bearing-housing half and on the opposite side at 15 into the inner end plates 17 and 18 of the frame. The plates 19 and 20 function as outer end plates. If the tunnel is moved towards the cylinders, as is illustrated schematically in FIG. 1, until the center line of the crank-shaft 2 comes to rest approximately on the edge 7 of the tunnel 1, it is clear, that near the point 6 insufficient stiffness of the cross section results due to a too small moment of resistance.

The frame, see the dotted lines in FIG. 1, should according to the invention be considerably strengthened and stiffened as is illustrated in FIG. 2. The same tunnel design from FIG. 1 is also shown here, the inner end plates 17 and 18 being present accordingly. The outer end plates 19 and 20 (FIG. 1) which form the boxes 21 and 22 in crank-shaft direction of the frame, are interconnected by the plates 23 and 24, to form a tubular girder 25, the cross walls being extended into the outer end plates. In case of a V-engine the end plates 19, 23 and 20, 24 form a sharp bend 35 on their meeting line. This tubular girder is extended from one side 26 of the engine to the other side 27, and is closed at both extremities. Due to a sufficient distance between the inner and outer end plates 17 and 19 respectively 18 and 20, a great stiffness can again be achieved allround the tunnel. In this tubular girder openings 28, 29 and 30 can be designed, without jeopardizing the stiffness, through which openings the inside of all tubular girder parts over the total length and Width of the frame, come into connection with each other, forming one integral flat box. By doing so the tubular girder 25 can be adapted as scavenging air receiver in case of the engine being a two-stroke engine.

Near 15 the stiffening rib of the tunnel opening merges into the inner end plates 17 and 18. These heavy end plates 17 and 18, extending over the total length of the engine, thus form an integral part with the edges 12, 13 and 14 of the tunnel. To conduct the large combustion forces from the cylinder heads along the shortest way with the maximum stiffness to the crankshaft main bearings, the cylinder head bolts are extended as tie rods into the stiff inner end plates 17 and 18. With 31 a cylinder head is indicated, with 32 a cylinder-liner surrounded by a cooling jacket, with 33 the cylinder head bolts or tie rods, a quantity of at least four per cylinder generally being fitted and at 34 being screwed into the inner end plate.

It should be noted that the above mentioned and other designs falling within the scope of the invention can be applied for welded, cast and also combined weldedcast constructions. The invention can be applied to engines in line, V-engines as shown in the example and also with engines with more than two cylinder banks. Furthermore the invention can also be applied to other engines than the common vertical type.

What we claim is:

1. In a tunnel-frame for a multicylinder internal combustion engine the improvement which comprises a plurality of cross walls, means defining in each cross wall a tunnel opening and a reinforced edge portion about said opening, a bearing housing fitted in each cross wall and disposed to receive a crankshaft of an engine, the size of the tunnel opening being sufficient for said crankshaft to be brought into and out from the frame along an axial path, said bearing housing including a non-removable portion that is integral with said reinforced edge portion, and a removable portion, the bore of said bearing housing being located at said reinforced edge portion and at a predetermined distance from the cylinders of the engine.

2. The improvement according to claim 1 including a tubular girder having bores that receive the cylinders of the engine, said tubular girder being interconnected with said cross walls.

3. The improvement according to claim 2 wherein said tubular girder has openings at said cross walls.

4. The improvement according to claim 3 wherein said tubular girder is disposed to function as a scavenging-air receiver.

5. The improvement according to claim 1 wherein said removable and non-removable portions of the bearing housing have fiat joints in a plane extending approximately through the center line of the bearing bore.

6. The improvement according to claim 2 wherein said cross walls in combination with the tubular girder have an approximately constant moment of resistance around the tunnel opening.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,901,206 Dated August 26, 1975 Jacob Hermanus Kuiper It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On page 1, item [75] the correct name of the inventor should be Jacob Hermanus Kuiper and the name Kuiper" should appear on the heading of each page.

Signed and Scaled this A ttes t:

RUTH c. MASON C. MARSHALL DANN Arresting Officer Commissioner of Patents and Trademarks 

1. In a tunnel-frame for a multicylinder internal combustion engine the improvement which comprises a plurality of cross walls, means defining in each cross wall a tunnel opening and a reinforced edge portion about said opening, a bearing housing fitted in each cross wall and disposed to receive a crankshaft of an engine, the size of the tunnel opening being sufficient for said crankshaft to be brought into and out from the frame along an axial path, said bearing housing including a non-removable portion that is integral with said reinforced edge portion, and a removable portion, the bore of said bearing housing being located at said reinforced edge portion and at a predetermined distance from the cylinders of the engine.
 2. The improvement according to claim 1 including a tubular girder having bores that receive the cylinders of the engine, said tubular girder being interconnected with said cross walls.
 3. The improvement according to claim 2 wherein said tubular girder has openings at said cross walls.
 4. The improvement according to claim 3 wherein said tubular girder is disposed to function as a scavenging-air receiver.
 5. The improvement according to claim 1 wherein said removable and non-removable portions of the bearing housing have flat joints in a plane extending approximately through the center line of the bearing bore.
 6. The improvement according to claim 2 wherein said cross walls in combination with the tubular girder have an approximately constant moment of resistance around the tunnel opening. 